If i try to conquer any planet I cant win the groundbattle, because there are 2 or more buildings which are invisible and invincible. So how can i conquer them?, anyone knows how to fix this?

you cant, best thing to do is to list what mod and version your using plus what planet it is, and what buildings if you can, so they can fix it.

Just hit the places where the invisible buildings are with bombing runs...

Just be thankful that you can do land battles, after i invade 3-4 planets the next planet i invade crashes the game.  Is there any way to disable the land battles?

Go into the Planets.xml file and set all of the values of to false.

(Exact XML is probably different, I am at work, but look for how Bespin is set up.)

Sweet. That's all I do in the demo, I don't bother with ground battle since the tutorial maps are much smaller than the actual release maps will be, so I only plays space battles (but that means I can conquer only a couple planets .